The invention relates to an image forming process of a novel silver halide light-sensitive photographic material for radiographic use. More particularly, a very sharp radiographic image forming process is described in which improvements are made in reducing deterioration of image sharpness which results from cross-over light on negative type silver halide light-sensitive photographic materials provided on both surfaces of a transparent support (hereinafter called the light-sensitive material).
Generally, most light-sensitive materials for forming radiographic images require satisfactory sensitivity and contrast. These requirements are satisfied by having light-sensitive silver halide emulsions coated on both surfaces of the support. However, image sharpness and contrast are found to deteriorate, primarily as a result of the "cross-over" phenomenon. This phenomenon results when radiographic light-sensitive materials coated both sides of the support are sandwiched between two fluorescent intensifying screens.
To be more concrete, light emitted from one of the fluorescent intensifying screens hits the silver halide emulsion layer directly contacting that screen. At the same time, the light is transmitted through the silver halide emulsion layer and the support thereof and hits the silver halide emulsion layer on the opposite side. The result is an image having poor sharpness.
The reason image sharpness deteriorates with cross-over light is that the image forming field is spread by optical refraction and by reflection diffusion in each of the fluorescent intensifying screens, silver halide emulsion layers, and supports.
Means for eliminating the above-mentioned cross-over light may be devised, such as that in which a support is colored or a reflective support is used. However, it has not been possible to eliminate or to reduce such cross-over light easily because sensitivity is lowered or an optical transmissive image cannot be obtained.
In recent years, silver saving attempts with light-sensitive materials have been intensified to stretch resources and reduce costs. In the case of radiographic light-sensitive materials, these `silver saving` activities have resulted in lowering the transmission density of an emulsion layer because of emulsion turbidity decreases. Consequently, the above-mentioned cross-over light increases; image sharpness deteriorates even further.
The present Applicants previously disclosed, in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese O.P.I. Publication) No. 48544/1979, a negative type silver halide light-sensitive photographic material containing the following items as a novel means capable of considerable saving in the amount of silver needed:
(1) light-sensitive silver halide particles, PA0 (2) metallic salt particles which are relatively more easily soluble than the above-mentioned light-sensitive silver halide particles (1), not substantially light-sensitive, and to which a dissolution retarder is adsorbed, and PA0 (3) physical development nuclei. PA0 (a) light-sensitive silver halide particles, PA0 (b) metallic salt particles which are not light-sensitive and which are more readily soluble in a processing solution than said light-sensitive silver halide particles, but whose surfaces are rendered less soluble than the light-sensitive silver halide by a dissolution retarder, PA0 (c) physical development nuclei, and PA0 (d) compounds comprising at least one kind of water-soluble dye having an absorption maximum in an aqueous solution of from 400 to 600 nm or a compound comprising said water-soluble dye coupled to a non-diffusive mordant, said processing solution containing PA0 (a) Light-sensitive silver halide particles, PA0 (b) Substantially non-light-sensitive metallic salt particles more readily soluble than the light-sensitive silver halide particles mentioned in (a) and on which a dissolution retarder is adsorbed, making the metallic salt particles less soluble than the particles in (a), PA0 (c) Physical development nuclei, and PA0 (d) Water-soluble dyes.
This light-sensitive material can also be utilized as a radiographic light-sensitive material as a matter of course, because it can have the necessary photographic characteristics such as high sensitivity, high contrast, and high maximum density even though only a small amount of silver is used therein.
Still, this light-sensitive material is not an exception to the above mentioned increase in cross-over light resulting from silver reductions; this material has serious disadvantages in that the image sharpness is poor.
Taking the above-mentioned factors into consideration, the present invention has been devised.
It is, accordingly, an object of the invention that, by making use of the aforementioned negative type light-sensitive material, image sharpness is improved by eliminating or reducing cross-over light.
Another object of the invention is to provide a method of processing a radiographic light-sensitive material in which sharpness is high, the silver is reduced, and decreases in sensitivity are not so great as to require that radiation doses be increased.